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UNITED STATES.

BENGT M. W. HANSON, OF HARTFORD, CONNECTICUT.

METAL-WORKING MACHINE.

Specification of Letters Patent.

Patented Mar. '7, 1922.

Application filed April 28, 1920. Serial No. 377,267.

To all whom it may concern:

Be it known that I, BENGT M. W. HANSON, a citizen of the United States,and a resident of Hartford, county of Hartford, State of Connecticut,have invented certain new and useful Improvements in a Metal-VVorkingMachine, of which the following is a specification.

The present invention relates in its more general application to metalworking machines adapted for, operation 'on curved surfaces, forinstance, machining or finishing the same, and has as its aim to soorganize the parts of the machine that the operations may be carried outon the work with the greatest efliciency, particularly as to accuracy,uniformity and expedition.

The various features of construction present in the machine will bedescribed with reference to their use in a machine for grinding holes,but it is to be understood that the present disclosure is by way ofillustration only and is not to be taken as restrictive of myconception, for while the invention has particular adaptability to thisuse, it is susceptible of other uses.

It has been the practice in grinding holes to employ a grinding wheelusually of less lengtlrthan the hole and supported at one side only, tofeed the work to the grinding wheel one step after the completion of oneout and before the commencement of a new one, and to move the grindingwheel in one direction-lengthwise of the hole during each cut so as togrind the hole from one end to the other. In accordance with theembodiment of the present invention, herein selected for illustrativepurposes only, the grinding wheel is supported at each end so as to besubstantially free from vibrations; the grinding wheel is preferablylonger than the hole which is being ground, and the work by preferenceis fed with a uniform motion to the grinding wheel during the grindingoperation so that the hole is uniformly ground throughout its length andno time is wasted in relatively feeding the work and tool; and thegrinding wheel is reciprocated longitudinally across the surface of thework so that a smooth finish is obtained; all of which is of advantageover the practice heretofore followed in that work of greater accuracyand finish may be had with a saving of time and labor.

In the accompanying drawings:

Fig. 1 is afront elevation of the machine,

the lower part of the broken away.

Fig. 2 is a right hand end view thereof, a portion of the pedestal beingin vertical section, taken substantially on line 22 of Fig. 1, and aportion of the gear box from which the Worlcholder is driven beingbroken away.

Fig. 3 is a top plan view.

Fig. 4 is a vertical sectional view taken substantially on line H, Fig.2, through the work support and the head and tail stocks, all otherparts being omitted except portions of the pedestal and the toolcarfiage which'are shown more or less in out- Fig. 5 is a side view of aportion of the upper end of the work support, a bearing ring 42 thereofbeing omitted, and the work chuck, the work and the tool being insection.

pedestal thereof being Fig. 6 is an enlarged detail view in frontelevation, with parts broken away, of the mechanism by which thereciprocating movement of the tool carriage is converted into rotarymovement of the work feeding cam.

Fig. 7 is a vertical sectional view taken centrally through thestructure shown in Fig. 6.

Fig. 8 thereof.

Fig. 9 is an enlarged detail view in vertical transverse section of theupper end of the work support.

Fig. 10 is a front view of the mechanism for feeding the work relativeto the tool.

Fig. 11 is a view of the mechanism for imparting a reciprocatingmovement to the tool carriage.

Fig. 12 is a view of an escapement ratchet clutch forming part of themechanism of Fig. 11, and

Fig. 13 is a vertical sectional view taken on line 13-l3, Fig. 3,through the tool carriage. 4

From Figs. 1, 2, 3 and 4, the general organization and arrangement ofthe principal parts of the machine maybe clearly seen. a is the pedestalhaving a fixed top plate 10 on which the tool carriage, designatedgenerally by the letter 6, is reciprocated in short strokes through theinstrumentalityof a suitably driven pinion 14 meshing with a rack 15 onthe tool carriage, as clearly shown in dotted lines Figs. 1 and 2. Onthis tool carriage are slidably supported, as hereinafter described morein is a horizontal sectional view holder, such as a chuck 71, carryingthe work ofvthe change s eed J) and its associated parts.

W, herein shown as being in the form of a bushing. The work support isswung in its bearings c to feed the work relativev to the tool, by meansof a feeding cam n cooperating with a roller 0 on the lower end of thework support 7. A spring 9 connected between the pedestal and the worksupport serves to maintain the roller 0, against the feeding cam.Preferably, the work V is fed with a uniform motion to the tool duringthe reciprocation of the latter, and to this end the reciprocatingmovement of the tool carriage b is converted into substantiallycontinuous rotary movement of the feedingcam by the device 7), hereinreferred to for convenience as a motion 'converting device. On the lefthand side of the machine is a gear box is from which is driven thepinion 14, and on the right hand side of the machine is mounted a gearbox Z, through the change Speed gearing of which the work holder orchuck z' is rotated at a relatively slow speed as will be hereinafterdescribed more in detail. The pulleys gearings may be driven in anysuita le manner as from a countershaft, not shown. The head stockspindle 11 carrying the toolis driven at a high rate of speed ,by belts32 passing about a drum 34 driven as by means of a belt 35 from the sameco-untershaft as that from which the speed change gearing is driven.

From the foregoing brief description, it

v will be understood that. the grinding wheel is rotated at a high rateof speed while the bushing is slowly rotated about its axis;

the grinding wheel is supported at its opposite ends so ias to be freeo-fvibration; the grinding wheel, while cutting, is reciprocated backand forth to insure uniform action and the work is fed with a uniform orcontinuous motion to the tool owing to the -cam-n being continuouslyrotated by the tool carriage b acting through the motionv convertingdevice 1).

Reference may now. be had more particularly to the construction of thetool carriage The tool carriage 12 comprises a main plate 16 slidable onthe top plate 10 of the pedestal a and having at each end and, ifdesired, intermediate its ends, standards 17 to which is secured a plate18 having in its under surface ways 19 slidably receiving the ways 20 onthe top surfaces of the bases of the head ving the pulley 31 on thecarriage. It is of advantage to supthe under port the head and tailstocks from surface of the plate 18 in that grit or the like, forinstanceemery from the grinding wheel, cannot gain access to the waysand gibs. It will be noted that the late 18 is inclined downwardly andforwardly so that any water or oil thrown onto the plate will readilyflow off. The head stock is moved longitudinally of the plate 18 intoand out of operative position relative to the work by the hand wheel 25fixed to a shaft carrying a :pinion 26 meshing with a rack 27L on thehead stock. Any suitable means for clamping the head and tail stocks inoperating positions may be provided, for instance binders 29 shown inFig. 2. The head and tail stocks carry suitable ball bearings 28supporting the spindles 11 and 12. On the head stock spindle 11 is afixed pulley 30 and on the tail stock spindle 12, a pulley 31 isfrictionally mounted for reasons hereinafter stated and these pulleysaredriven by the belts 32 passing about drums 34 and over suitableidlers 33 mounted in brackets carried by and extending rearwardly fromthe head .and tail stocks. The drums 34 are mounted at the rear of themachine and may be driven from a countershaft by means of belts 35 shownin dotted lines Fig. 3.

It is of advantage tosupport the opposite ends of the arbor of the wheelT on the spindles 1.1 and 12, to prevent vibration and chattering ofthe'wheel which result in uneven and faulty work.

In accordance with the present invention, the tail stock manner that thearbor of the grinding wheel may be brought into cooperative relationtherewith, .while the grinding wheel is rotating at high speed, withoutsetting up any influences tending to interfere with the smooth andregular rotary movement of the grinding wheel. This is accomplished, inthe present instance, by frictionally mount on the tail stock spindle,the friction between the s indle and the pulley being so adjusted thatit is very slightly greater than the friction offered by tlieb'earingsin which the spindle is mounted, and by driving the. pulley .31 at avery slightly greater speed than the head stock spindle 11. This meansthat when the spindle 12 is not supportingthe tool arbor, this spindleWill rotate substantially in unison with the pulley 31, i. e., at aspeed slightly greater than the tool arbor which is then being carriedonly by the rotating spindle 10, and when the rotating tool arbor isspindle 12, is driven in such brought into engagement with the spindle12, this spindle will slow down to the speed of the arbor and the pulley31 will run ahead of the spindle 12 without exerting enough drivingforce on the spindle to have any appreciable effect. With thisarrangement, it is not necessary to start and stop the rotation of thegrinding wheel when the tool arbor thereof is moved into and out ofengagement with the tail stock spindle. In one manner of speaking, theend of the grinding wheel arbor has a bearing in the spindle 12 and thisspindle is in the nature of a rotating bearing member which is so driventhat it exerts no drag or wear on the arbor.

While in the preferred embodiment illustrated in the drawings the pulley31 is frictionally mounted on the tail stock spindle 12 and is driven ata slightly greater speed than the head stock spindle, if desired thearrangement ma be such that the tail stock spindle and the head stockspindle are positively driven at the same speed.

The work suppoi t f has laterally extend- 7 ing trunnions 40, the outerends of which are supported in bearings e on the front of the pedestala. In the circular head 13 of this support is fixed a pair ofcomplementary bearing rings 41, 42, between which is supported a rotaryring 43 carrying the chuck 2' which may be of any suitable construction.It will be noted that the opposed bearing faces of the rings .41, 42,are inclined towards one another, this being of advantage in that arelatively large bearing surface is provided for the ring 43 withoutincreasing the width of the head of the work support. A ring like gear-44 having a bearing on the bearing ring 41 is driven, as most clearlyshown in Fi s. 2 and 4, through the gears45 by the s aft 1" which isconnected to the change speed gearing Within the gear box Z. The gear 44is yieldingly or flexibly connected to the ring 43 so that the ring 43will run smoothly and regularly, free from any disturbances resultingfromthe driving mechanism therefor, and to this end, as shown mostclearly in Figs. 5 and 9, the periphery of the ring 43 is interrupted bynotches 46 which receive small blocks 47 of a yielding material such asleather and each of these blocks is secured to the gear 44 by screws 48-The associated rings 49 form oil guards which may be of any suitableconstruction.

Reference will now be had to the means for feeding the work to the tool.This means, as stated, comprises in part the feeding cam 'n having aspiral circumference cooperating with the roller 0 on the dependlng legof the work support 7. This cam is fixed on the shaft 55 journaled inthe forward end of-a slide 56 mounted on a suitable support 57 which maybe a part of the pedestal a. For the purpose of adjusting the slide 56and thereby roughly adjusting the Work support and the work carriedthereby to the tool, a screw 58 journaled in a bearing on the support 57and having threaded engagement with the slide 56 is provided and thisscrew is connected by gearing 59 including the shaft 60 to a'shaft 61on'the forward end of Which is a hand wheel 62. Fixed to the shaft 55 isa worm gear 63 with which meshes a worm 64 splined on a shaft 65connected through bevel gears 66 and a shaft 67 to a shaft 68 passingthrough the device 10 and carrying on its forward end a hand wheel 69whereby the cam 11 may be angularly set with respect to the roller 0 ofthe Work support.

The motion converting device p from'v which the shaft 68 (through whichthe feeding cam n is driven) derives its motion from the reciprocatingmovement of the tool carriage b, is most clearly shown in Figs. 6, 7 and8. Secured to the tool carriage b is a plate 72 to which is pivoted forangular adjustment a guide member 73 adapted to be locked in adjustedposition by a screw 74. On the outer face of the guidemember 73 is adove-tail groove in which works a block 75 adapted to be detachablysecured by means of a pin 76 to the head of the recipro-' cating member77 having a pair of opposed racks 78, 79, straddling the shaft 68. Thisreciprocating member is housed within a casing'81 and is normally urgedupwardly by the spring pressed plunger 82. Carried by the shaft 68 is aratchet wheel 83 having a. hub at each side upon which are freelymounted segmental gears 84 meshing with the respective racks 78, 79.Each of these segmental gears has an arm on which is pivoted a pawl 85,both pawls being headed in the same direction and cooperating with theratchet wheel'83. It will be readlly observed that when the toolcarriage is moving to the right, referring to Figs. 1 and 6, the guidemember 73 moves therewith, the block 75 will ride down the groove in theguide member resulting in therack member 77 moving downwardly, the rearsegmental gear 84 with Which rack 79 is in mesh will be rotated in aclockwise direction, and since the pawls 85 are active when moved inthis direction, the shaft 68 is rotated. In the meanwhile, the rack 78is rotating the front segmental gear counter-clockwise and the pawl 86thereof rides freely over the teeth of the ratchet wheel. When the toolcarriage moves to the left, the member 77 will move upwardly and therack 78 will move the front segmental gear 84 clockwise, resulting inrotation of the ratchet wheel and the shaft 68 in the same direction aswhen the rack member 77 was lowered. Thus, on movement of the toolcarriage in either direction, the shaft 68 and the feeding cam driventherethrough will be rotated subvaried by angularly adjusting the guidemember 73. The more nearly the groove of this guide-member is to ahorizontal plane,

the slower is the rate of rotation of the feeding cam.

.It may be desirable in some, instances, instead of thus feeding the iwork to the tool during the cutting operation,- to follow the practiceheretofore used of feeding the work to the tool with a step by stepmovement, and take successive cuts in the work.- To this end thearrangement is such that the rack member 77 of the device 10 may bedisconnected from the block 75 and connected to a mechanism which isactuated only when the tool carriage reaches the'ends of its strokes. Asherein -shown, this mechanism comprises a link 87 pivotally carried by abracket on the pedestal aand connected at one end through link 88, crank89 and link 90 to a lever 91, pivoted, as shown, to the pedestal a andhaving its upper end positioned between a pair of dogs 92 adjusta-blycarried by the tool carriage b. The opposite end of the link 87 isadapted to be detachably connected to the rack member 77 by means of thepin 76 or in any other suitable manner, A c mpression spring93 isprovided for holding the link 87 so that it will not be in the way whenthe rack member 77 is connected to the block 75.

The driving mechanism for imparting a reciprocating movement to the toolcarriage may be of any suitable construction, but for illustrativepurposes, I have shown more or less conventionally a mechanism 1n Fig.

11 which may be used to advantage. On the lower end of the shaftcarrying the pinion 14 is a bevel gear 94 meshing with oppositelydisposed bevel gears 95 on a shaft 96 driven through suitable speedchange gearing within the gear box is, this gearing not being shown asit may be of any suitable type. On the main shaft 97 of the speedchanging mechanism' within the gear box is, is a ratchet wheel 98 withwhich cooperates a spring pressed pawl 100 carried by a'disk 101 fixedto a cam shaft'102 having a cam groove in which operates a rollercarried by a shipper 103 associated as shown with the clutches 104;of.the bevel gears 95. The pawl 100 is controlled by an escapement yoke105 slidable on a pin 106 and connected by a rod 107 to a lever 108which, in turn, is connected 'by a link 109 to the lever. 91. It will bereadily understood that when the tool carriage reaches either end of itsstroke, the escapement yoke is moved to withdraw one .end thereof fromthe pawl and bring the other end of the yoke into the path of the pawlthus permitting the pawl to intermitto move the slide 56 with the roller0 against tently cooperate with the continuously driven ratchet wheel98, whereby the cam shaft 102 is intermittently rotated through one-halfrevolution and the shipper is shifted to actuate the clutches 104 andalternately connect thebevel gears to the shaft 96.

To set up the machine for a given piece of work, a .test piece, having ahole of some what less diameter than that to which the hole in the workis'to be ground, is positioned with the chuck 6;, either the changespeed gearing of the driving mechanism for reciprocating the toolcarriage is thrown out of operation orthe motion converting device p isdisconnected so that it will not be operated upon reciprocation of thetool carriage and therefore the feeding cam n will not be automaticallyrotated during operation upon the test piece; the head stock 0 ismovedto position the grinding wheel with-. in the'hole in the testpiece; the high point of the feeding cam n is brought into engagementwith the roller 0 on the depending leg of the work support f by manuallyturngearin within the gear box Z is thrown into operation to effectrotation of the chuck z carryin the test piece; (it will be remembered tat due to the-manner in which the tail stock spindle 12 is driven it isunnecessary to interfere with the rotation of the grinding wheel when itis desired to move the same into and out of operative position) then theoperator by manually turning the hand wheel 62 slowly moves the slide 56on which the feeding cam n is jour naled to feed the test piece to thegrind ing wheel, and the operator continues so the high point ofthe'feeding cam until he has determined by measurement that the hole inthe test-piece has been ground to the same diameter as that to which thehole in the work is to be ground.

WVithout disturbing the position of the slide 56, the test piece is nowtaken out of the chuck z and the bushing or work lV inserted in itsplace; the reciprocating member 77 of the device 72 is connected to theblock 75, and the feeding cam n is manually rotated by means of the handwheel v62 to bring the low point of the cam n into engagement with theroller 0 on the work support; the grinding wheel T is moved intooperative position within the hole in the work, and then the drivingmechanisms for reciprocating the tool carriage b and rotating the chuck2' are thrown into operation and the grinding proceeded with. Thefeeding cam is continuously or uniformly rotated in the direction of thearrow, Fig. 2, due to the reciprocating movement of the tool carriage bacting through the motion oonverting device ;0 as heretofore describedin detail. Thus, it will be seen that the grind- 130 scribed, arotatable work holder, a grinding ing wheel is lon itudinallyreciprocated back and forth wh1le operating throughout the entire lengthof the bushing and during such reciprocation-of the grinding wheel thework is fed thereto with a uniform motion. When the feeding cam has beenrotated to the extent that the high point thereof reaches the roller 0on the work support, it is of course evidentthat the hole in the work isof the correct .size, for this cam is now in the same position as whenthe grinding operation on the test piece was terminated, it beingremembered that, after operation on the test piece the adjustment of theslide 56 is not disturbed.- After the machineis set for grinding onehole, it will grind the holes of all subsequent pieces to the same exactsize.

It is of course evident that my invention is susceptible of variousmodifications and changes which are within the spirit of the inventionwithout departing from the scope of the following claims, it beingunderstood that the present disclosure of my invention is by way ofillustration only and it is not to be taken as restrictive of myconception.

What I claim is:

1. In a machine of the character described, a rotatable work holder, agrinding wheel, means for rotating said holder, means for reciprocatingsaid grinding wheel and holder longitudinally one relative to the otherduring the grinding operation, and means for uniformly feeding saidgrinding wheel and holder one relative to the other during suchreciprocating movement.

2. In a machine of the character dewheel, means for rotating said worksupport and grinding wheel, means for reciprocating said grinding wheellongitudinally of the work holder, and automatically operated means forfeeding the work relative 'to the grinding wheel, both of said lastmentioned means being operated during the grinding operation.

' 3. In a hole grinding machine, a work holder. a grinding wheelextending through the hole in the Work and supported at each side ofsaid work holder, means for rotating said grinding wheel, and means forcontinuously feeding said Work holder and grinding wheel one relative tothe other during the grinding operation.

4. In a hole grinding machine, a rotatable work holder, a grinding wheelextending through the hole in the work, means at each side of said workholder for supporting the opposite ends of said grinding wheel, means.for reciprocating said grinding wheel across the surface of the work,and means for feeding said work holder relative to said grinding wheelduring the cutting operation of the latter.

5. In a hole grinding machine, a rotatable 'through and of greaterlength than the hole to be ground, means at each side of said workholder for supporting the opposite ends of the grinding wheel, meansforreciprocating the grinding wheel longitudinally across the surface ofthe work, and automatically operated means for uniformly feedingthe workto the grinding wheel during the grinding operation.

7. In a hole grinding machine, a work support, a tool carriage having ahead stock and a tail stock mounted thereon and supporting a tooltherebetween, means for reciprocating said tool carriage, and meansactuated by the reciprocation of said tool carriage for uniformlyfeeding the work relative to the grinding wheel during the entire extentof travel of said tool carriage.

8. Ina hole grinding machine, a slidable carriage, a head stock and atail stock carried thereby, a tool supported therebetween,-

9. In a hole grinding machine, a tool carriage, means for reciprocatingthe same, a

work support, and means actuated by the reciprocating movement of saidtool carriage for uniformly feeding the work support relatively to thetool during the reciprocation of said tool carriage.

10. In a hole grinding machine, a carriage, means for reciprocating thesame, a head stock and a tail stock on the carriage, a tool supportedtherebetween, a pivoted work support including a rotatable work holderpositioned between said stocks and encircling said tool, and meansoperated by the reciprocating movement of said tool carriage foruniformly swinging said support about its fulcrum to uniformly feed thework to said tool.

11. In a machine of the.character described, a tool carriage, a toolthereon, means for reciprocating the tool carriage, a pivoted worksupport, a rotatable work holder thereon, means for rotating said workholder, means cooperating with said work support for swinging the sameabout its fulcrum to feed the work to the tool, and a motion convertingdevice between the tool carriage and feeding means for unifor uniformlyoperating said feeding means during reciprocation of the carriage, saiddevice including means for varying the rate of feed of the work to thetool.

13. In a machine of the character described, a tool carriage, a toolthereon,

means for reciprocating said carriage, a pivoted work support, arotatable work holder thereon, means for rotating said work holder,

means for rotating said cam.

- ing said slide,

a feeding cam cooperating with said work support for swinging the sameabout its fulcrum to feed the-work to the tool, and means between thetool carriage and the cam for uniformly rotating said cam during thereciprocation of said carriage.

14. In a machine of the character described, a work support, a camcooperating therewith, a slide in which said cam is journaled, means foradjusting said slide, and

15. In a machine of the character described, a work support, anactuating cam therefor, a slide in which said cam is jour naled,manually operable means for adjustand automatically operated means forrotating said cam.

16. In a machine of the character described, a tool carriage, a pivotedwork support, a cam in cooperative relation with said support, a slideon which said cam is ournaled, means for adjusting said slide, and meansoperable by said tool carriage for rotating said cam. 4

17. In a machine of the character described, a horizontally extendingmember, and a tool stock slidably supported from the under side of saidmember.

18. In a machine of the character described, a forwardly inclinedmember, a tool stock having a base'portion positioned beneath saidmember, and cooperating ways on the under side of said member and thetop of said base portion.

19.. In a machine of the character described, a tool carriage includinga base havstock having a base ing spaced standards arising therefrom anda plate secured on said standards, a tool portion positioned beneathsaid plate, and cooperating ways on the underside of said plate and thetop of said base portion of the tool stock. 20. In a machine of thecharacter described, a pair of spindles cooperatively positioned tosupport a part therebetween,

bearings therefor, means for positively driving one of said spindles,and means for frictionall driving the other of said spindles.

21.--n a machine .of the character described, a head and a tail stockspindle, bearings therefor, means for positively driving. the head stockspindle, frictional driving means normally tending to drive the tailstock spindle at a slightly greater speed than the head stock spindle,the frictional 'said tail stock spindle and the bearing therefor.

23. In a machine of the character described, a reciprocating toolcarriage, a work support, rotatable means for feeding said work support,means for converting the reciprocating movement of said carriage intorotary movement of said feeding means, means adapted to be detachablyconnected to said device and actuated by said tool carriage at the endof each stroke for rotating said feeding means step by step, and meanscarried by the tool carriage and adapted to be detachably connected tosaid device for uniformly rotating the feeding meansv dur ingreclprocation of said carriage.

24. scribed, a reciprocating carriage, a guide member thereon having agroove, a .slidev block in the groove, means including a sta- In amachine of the character de-' tionarily pivoted lever actuated by saidcarriage at the end of each stroke thereof, a

work support, rotatable feeding means there- I for, a motionconverting'device associated therewith and having a reciprocable rackmember, and means for detachably connecting said lever or said block tosaid rack member. 7 4

25. In a machine of the character described, a spindle, a rotatingbearing member cooperatively positioned relative thereto, a partconnectedto said spindle and having a bearing adapted to rotate in saidbearing vmember, and means for driving said spindle.

26. In a machine of the character describefi), a spindle, a rotatingbearing mem- I her 0 peratively positioned relative thereto, a partconnected to said spindle and hav-. ing a bearing freely rotatable insaid bearing member, means for driving said spindle,

grid means for rotating said bearing mem- 27. In a machine of thecharacter described, a spindle, a rotating bearing member cooperativelypositioned relative thereto, a part connected to said spindle and havinga bearing in said bearing member, means for driving said spindle, andmeans for frictionally driving said bearing member.

28. In a machine of the character described, a spindle, a bearing membercooperatively positioned relative thereto, bearings for said spindle andbearing member, means for positively driving said spindle, andfrictional driving means normally tending to drive said bearing memberat a slightly greater speed than said spindle.

29. In a machine of the character de? scribed, a pair of alined spindlespositioned to support a member therebetween, driving means at each endthereof, one of said driving means being frictionally mounted on one ofsaid spindles and adapted to be driven at a different speed relative tothe other of said driving means.

30. In a machine of the character described, a pivoted Work support, arotatable cam cooperative with said Work support to rotate the latterabout its axis, and a slide supporting said cam and adjustable at rightble Work holder adapted to support tubular pieces of Work, a grindingWheel extending into and surrounded by said holder, means for rotatingsaid holder, means for reciprocating said grinding Wheel longitudinallyrelative to said holder during the grinding operation, and means foruniformly feeding said holder relative to said grinding Wheel duringsuch reciprocating movement.

BENGT M. W. HANSON.

